I need a hint to model a modern heater radiator
Depending on the amount of detail you need, it is rather easy to model.
I made this in just a few minutes (took me longer to write this answer).


First break down the object, and think about each part.
There are nine fins (and it looks the same front and back), so use a plane Solidify, Array and Mirror modifiers to make those. 

The bottom corner is beveled on all of them, so before applying the array modifier bevel the bottom vertex CtrlShiftB.


Add a plane as a separate object to use as the back.


Back in the original object, now with the mirror modifier applied, start editing the individual fins. Move the center three up. Extrude the bends for the inside ones, and extrude the outside frame.


Just add two cylinders, and bevel the remaining corners, and tweak the shape.

It really pretty easy. Use the modifiers! Solidify and Mirror are a must for this object.